The invention relates to residential branch circuit breakers, which are the molded case, narrow width type, usually one inch or three quarters inch, such as shown in U.S. Pat. No. 3,081,386. These breakers are normally utilized in residential and commercial applications up to 240 volts.
Circuit breakers, and the panelboards or load centers to which they are mounted, are designed to be compact and physically compatible with existing apparatus. However, electrical utilities are providing increased available current in new installations. As a result, the short circuit interruption capacity requirement of narrow width circuit breakers has increased from 10,000 amps to 22,000 amps for new breaker designs, while existing apparatus designs place sever limitations on changes in physical arrangement and size.
In contrast, industrial breaker designs do not have such size constraints, and their much higher circuit interruption capacity involves different design criteria.
The present invention provides a residential breaker incorporating a magnetically permeable slot motor mounted within the narrow width case and around both current carrying conductors. Current flows through the conductors in reverse parallel opposite directions to develop magnetic repulsive force which is concentrated by the slot motor and urges separation of contacts. The slot motor is a U-shaped member receiving both conductors therein from one side. Increased short circuit interruption capacity is provided without resorting to wide case design or otherwise resorting to industrial breaker type design.